I really like the APC 15.75x13x3 props. Beside the 90" P-38, I used that prop on a ESM Skyraider, & FW-190 both 10S setups, and am still using one on a 8.5 pound 60 size Corsair on 6S, and they all flew great. The KV on the Corsair is slightly lower than yours with a 6000RPM no load speed. It is a very nice enjoyable scale speed. The Corsair is lighter, and has a lot of wing area than your P-38, so I think your 325KV motors on 6S with the APC props would also be a great combo. I think you want a little more speed avalible. What has me concerned with that setup is the 1110 watt rating. Pretty sure you are going to exceed that a lot of the time.
Master Airscrew has a lot of choices, G sonics are very nice props.
Maybe do your first couple flights with a pair of APC 15x10E or 14x12 thin electric two blade props. Would be no question they are going to give you enough thrust, speed, and no overtaxing your motors. Can use the flight data form those flights to help pick the right props. Just leave the spinners off until you pick the final props, helps keep the motors cool anyways....just a thought
http://www.ecalc.ch/motorcalc.php?ecalc&lang=en